Timney Drop-In single stage Match Trigger with solid straight trigger. For Standard .154 Pin Receiver. The trigger is factory preset with a pull weight of 4. Installation is quick and no adjustments are necessary, 100% true drop-in trigger.Lightweight, 6061 T6 alloy housing is anodized for superior durability. Hammer is EDM machined from S7 tool steel that combines hardness to resist wear with superior impact resistance to withstand heavy use without chipping or breaking. Finally, a Teflon Nickel coating is applied to the hammer to deliver a super smooth trigger pull with superior lubricity. Other components are EDM cut from A2 tool steel, then heat treated to RC 56-60 for longer service life. The proprietary design eliminates pin rotation and walkout.